Chapter 6 - Energy Flashcards
Define Energy
Capacity to do work
Principle of Conversation of Energy
Energy cannot be created or destroyed, it can only be converted.
Why there is energy lost in non-ideal swinging pendulum?
Kinetic Energy convert to Thermal energy and Sound energy when pendulum experience air resistance and friction.
The thermal and sound energy is dissipated to the surroundings
They cannot be converted back in to G.P.E or K.E, result in energy lost.
In real life, useful energy output is always LESS than energy input, why?
Energy will be dissipated due to friction as a form of sound and thermal energy
Energy lost is considered _____ energy output
Wasted
Total Energy Input =
Useful energy output + Wasted energy output
Efficiency =
Useful energy output/ Total energy input x 100%
Work Done =
Force x distance moved in the direction of the force
When a boy is pushing a tree, but the tree stay stationary, is there work done?
No.
Kinetic Energy =
1/2 x mass of body x speed of body^2
To lift up an object Potential Energy (Work) =
Force x Distance travelled = Weight x Height = Mass x Gravitational Field Strength x H
Define Power
Rate of work done/ Rate of energy conversion
I.S Unit for Power
Watt (w) (Joule/second)
Power =
Work done / Time
Energy converted / Time
